This invention relates to a method of and an apparatus for producing an electromotive force as soon as an elevated temperature is sensed as a result of a fire, and more particularly to novel method and apparatus of the character in which the apparatus can be actuated with certainty and without errors even if external electric supply is unexpectedly interrupted at the time of a fire, providing highly reliable safety means on such occasions.
There are hereto known fire alarms or emergency lights which are mostly actuated by external commercial electricity, self-contained dry cells or secondary cells. However, it is very likely that the commercial electricity may be cut off at the time of a fire. Furthermore, it is known that the dry cell or secondary cell will be unreliable with regard to its working life or durability if it is not in service for a long period of time, and therefore needs very careful and costly maintenance and inspection service during that period.
There is also known a single-function fire alarm which is exclusively intended to produce warning sounds. An overall or plural-function fire alarm system is also known, but it cost so high that it is difficult or impossible to install one at home in general.